Low reluctance magnet core and method of manufacturing the same



A nl 30, 1957 A. J. HILGERT 2,790,937

LOW RELUCTANCE MAGNET CORE AND METHOD OF MANUFACTURING THE SAME Filed Oct. 4, 1951 2 Sheets-Sheet 1 fg j.

a L L fave/Lian iv ,g o/gdolfifi rffii gerz data 10%? April 30, 1957 HlLGERT 2,790,937

LOW RELUCTANCE MAGNET CORE AND METHOD OF MANUFACTURING THE SAME Filed Oct. 4, 1951 2 Shoots-Sheet 2 Patented; Apr. 30, 1957 LGW RELUCTANCE MAGNET CORE AND b IETHQD 6F MANUFACTURING THE SAME Adolph J. Hilgert, Milwaukea wis, assignor to lliaso Inc., Milwaukee, Wis, a corporation of Wisconsin Application October 4, 1951, Serial No. 249,778

7 Claims. (Cl. 317-153) This invention relates, in general, to thermoelectrically powered control devices, and has particular relation to an improved low reluctance magnet core for use in the power unit for such devices.

Due to the minute character of the maximum thermoelectric power (i. e., of the order of about 5 milliwatts) that can be produced by the heat of the flame of a gas burning pilot burner on the single hot junction of a single thermocouple, it has heretofore been necessary Where it has been desired to move an armature through a distance, and thus perform work, to use a thermopile (i. e., a plurality of thermocouples joined in series) for thermoelectrically energizing the electromagnet. The work performed may be to open a main valve member as more fully disclosed in the copending: application of Russell ll. Matthews, Serial No. 246,464, filed September 13, 1951, now Patent No. 2,717,381, or for operating a pilot'valve mechanism to control an automatic diaphragm valve as more fully disclosed in the copending application of Donley S. Collins, Serial No. 245,232, filed September 5, 1951, now abandoned, or to operate a thermoelectrically controlled switch or accomplish any other similar purpose.

One of the main objects of the present invention is to provide a new and improved power unit which isadapted" to be thermoelectrically powered. sufficiently by the heat of the flame of a gas burning pilot burner on the single hot junction of a single thermocouple to move an armature through a distance and thus perform work such as previously mentioned. v

Another object of the invention is to provide a new and improved thermoelectrically powered magnetic operator or power unit comprising an improved core structure provided with core posts around which the coil is wound, and which core posts have enlarged ends or pole pieces for increasing the initial pull but without appreciable joints between the core posts and the pole pieces deleteriously to affect the magnetic flux path.

Another object of the invention is to provide in a power unit for thermoelectrically powered controls a core structure and coil arrangement of the character set forth, and more particularly a core structure and coil arrangement of this character in combination with a pivot bracket accurately correlated with respect to the core structure and on which an armature arm connected to a control member is pivoted independently of the magnetic frame or core structure which is utilized in its entirely as the magnetic flux path, all to the end of enabling energization of the operator by a single thermocouple sufficiently to operate the control member.

Another object of the invention is to combine the improved power unit with a control member and with a single thermocouple having a single hot junction whereby to operate the control member by thermoelectric energiz'ation of the power unit by the heat of a ga s-burnijng pilot burner on the single hot junction of the single thermocouple. I I, I

Further objects and advantages, and numerous adaptations of the invention will appear from the following detailed description, takenin connection with the accompanying drawings.

In the drawings:

Figure 1 is an elevational view of a power unit embodying the present invention, and showingthe'armature'arm of the device connected to operate a pilot valve mechanism and a single thermocouple connected in circuit with the coil wire and positioned where its single hot junction will be heated by the flame of a gas-burning pilot burner;

Figure 2 is a top plan view' of the power unit;

Figure 3 shows the step of expanding the ends of the core posts in openings in the pole pieces;

Figure 4 is an elevational view of the core after joining the pole pieces to the core posts, and after application of insulating washers; and

Figure 5 is a top plan view of the core structure shown in Figure 4.

Referring now to the drawings, the embodiment of the invention selected for illustration is in the form of a thermocouple powered electromagnetic operator for controlling a diaphragm valve, for example, of the type more.

fully disclosed and claimed in the copending application of Donley S. Collins, Serial No. 245,232, filed September 5, 1951.

The pilot valve means and electromagnetic operator selected for illustration comprises a main base plate 1. A pair of bleed port member 2 and 3 have coplanar attachments to one side of the base plate 1 and project from the base plate with their axes in laterally offset parallel relation. The attachment of the bleed port mem bers to the base plate may be accomplished by screwing their lower threaded ends 4 into ports 5 and 6 in the base plate. Shoulders at the upper ends of the threaded ends 4 may be precision formed or finished to seat against a precision formed upper surface of the base plate 1 to assure proper correlation of the bleed port members 2 and 3 relative to each other and relative to the base plate 1.

A pivot bracket 7 of generally L-shaped form has its base attached at 8 to the plate 1 substantially coplanar with the attachment of the bleed port members to the base plate. By precision surfacing the base of the bracket 7, its desired correlation with respect to the base plate It and the bleed port members 2' and 3 is assured. The base of the bracket 7 may be secured to the plate 1 by screws, or by welding, or otherwise as desired.

An armature arm 10 is pivoted at 11 on the upper end of the bracket 7 for pivotal movement, for example, from position closing the upper end of the bleed port member 2 and opening the other bleed port member 3 to position opening the upper end of the bleed port member 2 and closing the upper end of the bleed port member 3, and vice versa. The pivot 11 is preferably provided by a pair of screws 12 carried for adjustment by the armature arm 10. The scre. 's 12 have pointed ends, one seating in a conical pivot seat 12' in the upper end of the bracket 7 and the other in a V-shaped groove in the upper end of the bracket 7. A contractile spring 13 is connected at one end to the armature arm 10, and at its other end to the base plate 1. This spring 13 yieldingly urges or biases the armature arm 10 to retracted position closing the bleed port member 3 and opening the bleed port member 2 as shown in Figure l.

The armature arm ll) preferably carries, for adjustment therein, screws 14, and these screws carry valve seat members 15. The valve seat members 15 are preferably formed of steel or other relatively hard material, and the bleed port members 2 and 3, or at least their upper ends which cooperate with the seat members 1-5, are preferably formed of aluminum or other relatively softer material. This permits coining or adaptation of the" upper ends of the bleed port members 2 and 3 to the valve seat members in the operation of the device, thus providing self-correction and tight seals.

The thermocouple powered electromagnet operator has a core having a pair of parallel core posts with separate enlarged pole pieces 21 and 22 at their upper ends and a common pole piece 23 at their lower ends.

In one illustrative embodiment of the invention and without limiting the claims thereto, the core posts 20 are of cylindrical form of a diameter of about W of an inch and of a length of about 1% inches. Each of the pole pieces 21 and 22 is of circular form of a thickness of about A; of an inch and of a diameter of about of an inch. The pole piece 23 is of a thickness of about Ms of an inch and is of oblong form of a length of about 1 /1 of an inch, with rounded ends conforming with the rounded ends of the pole pieces 21 and 22.

Where the core posts and pole pieces are formed of metal or alloy which is difficult to machine such, for

example, as Alleghany 4750 (which is a metal corn 2 posed of about 50% nickel and 50% iron)-the pole pieces 2.1, 22, and 23 are formed with openings 24 there in of diameters tightly to receive the ends of the core posts 20. The ends of the core posts are then inserted through these openings, as shown more or less diagrammatically for one core post in Figure 3, and with the outer ends of the core posts 20 projecting from the openings 24 as shown at 25. The core post 20 is then gripped between the pole pieces 21 and 23 to support the same, and preferably in a fixture shown diagrammatically in dotted lines at 26. The fixture 26 fits between the pole pieces 21 and 23 and holds them against movement toward one another, and also prevents the core posts from expanding radially between the pole pieces when pressed or struck.

The next step is to expand the ends of the core post 20 into the openings 24. This may be accomplished, for example, by placing one projecting end of the post 20 against an anvil 28 (Figure 3) and striking the opposite projecting end 25 with a hammer or other suitable tool 29 to expand the ends of the post 20 in the openings in the pole pieces and into secure engagement with the pole pieces. The core posts and pole pieces are then heattreated, preferably in an hydrogen atmosphere, at a temperature above about 2000 F., and thereafter slowly cooled for approximately two to four hours. This treatment anneals the core structure and, with the previous expansion of. the ends of the posts into the pole pieces, deforms and joins the grains of metal. so that the core posts and pole pieces are substantially in one piece, which reduces the reluctance and improves the magnetic flux path.

Where the core posts and pole pieces are formed, for example, of relay steel which is cheaper and will permitthe core posts and pole pieces may be formed in one piece within the scope of the broader aspects of the present invention.

After completing the core structure, the coil 32 is wound around the posts 20 and between the pole pieces. As an illustrative example, the coil 32 for the previously described core structure may comprise 44-0 turns of approximately No. 19 gauge copper wire. Insulating washers 33 may be cemented to the magnet frame, and the posts may be wrapped with kraft paper or other suitable material before winding the coil 32. Radially opening notches or openings 34 in the washers permit them to be slipped into place over the posts 20 after the pole pieces are joined to the posts. The openings 34 also permit the coil wire to be led to and from wound position on the core posts 20.

For purposes of. exemplification, a relay or electromagnetic operator of the type described, is adapted when energized by a single thermocouple heated by a gas-burn ing pilot burner under fire box conditions to actuate the armature arm 10 to attracted position, thereby closing the upper end of the bleed port member 2 and opening the upper end of the bleed port member 3. The maximum that a single thermocouple is capable of producing under such conditions is approximately 32.0 milliamperes at approximately 35 millivolts or thermoelectric power of the order of approximately .34 milliwatts. Due to the limitation of this thermoelectric energy to a relatively minute amount and the inability to electromagnetically operate the device with such energy, it has heretofore been the practice to employ a thermopilc comprising a number of thermocouples joined in series, or other means for accomplishing the desired results.

The base of the core of the operator or power unit is attached to the main supporting base 1 coplanar with the attachment of the bleed port members 2 and 3 and bracket 7 to the base. This assures proper correlation of the op orator relative to the base 1; also relative to the pivot bracket 7, and relative to the bleed port members 2 and 3. T he attachment is obtained by attaching the bottom pole pieces 23 to the base 1, for example, by screws, one of which is shown at 36 in Figure 1.

While one pivot screw 12 is referred to in the preceding description, it will be noted that there may be two such screws as indicated in Figure 2. The magnetic operator is provided with an armature 37 at least equal in area to the pole faces of the upper pole pieces 21 and 22, and the magnetic flux path is adapted to be completed through this armature. The armature 37 is attached to the under side of the armature arm 10, for example, by screws 38 as shown in Figure 2.

As more fully disclosed in the copending application of Donley S. Collins, the pilot valve means controls a diaphragm valve (not shown) which, with the bleed port member 2 open and the bleed port member 3 closed, operates to closed position to shut off the flow of gaseous fuel to a main burner 40. Movement of the armature 37 to attracted position closes the bleed port member 2 and opens the bleed port member 3, and the diaphragm valve then opens under pressure of the gaseous fuel. This description of these features is believed to be sufiicient since per se they form no part of the present invention.

The gaseous fuel supply pipe 42, in which the diaphragm valve (not shown) is disposed, leads to the main burner 40 and delivers gaseous fuel thereto, preferably through a mixing chamber 43 to which air is admitted through. adjustable air inlets (not shown) as well understood in the art.

A pilot burner 45, which is located in juxtaposition to the main burner 40 to maintain a pilot flame for igniting the main burner, is supplied with gaseous fuel by a pilot tube supply pipe 46. The positions of the pilot burner flames are shown in dotted lines for purposes of illustration.

Thermoelectric power for energizing the operator to move the armature 37 to attracted position with accompanying movement of the valve seat member 15 for the bleed port member 2 to closed position, and movement of the other valve seat member to open position, is supplied by a single thermocouple 50. The thermocouple 50 comprises a pair of dissimilar thermocouple members 51 and 52, one formed, for example, of Chromel or other suitable material, and the other formed of copel or other suitable material separated in the thermoelectric series from the material from which the other member is formed. Where the thermocouple is of the general type disclosed and claimed in Oscar J. Leins Patent No. 2,126,564, patented August 9, 1938, the outer tubular thermocouple member will be formed of Chromel or other material similarly related to the material of the inner thermocouple member.

The thermocouple members 51 and 52 are joined at 53 to form a single hot" junction which, in use, is positioned to be heated by the flame of the pilot burner 45. The thermocouple is connected in series with the coil 32 of the operator, for example, by connecting one of the cold junctions of the thermocouple with one end of the coil 32 by a lead conductor 55. The other cold junction of the thermocouple may be grounded as at 56, and the other end of the coil 32 may be grounded at 58.

As previously indicated, the thermocouple 50 preterably has a resistance which, with the resistance of the lead conductor, is substantially equal to the resistance of the coil 32 of the operator.

In the operation of the device, when the flame of the pilot burner 45 is extinguished, the operator is deenergized and the spring 13 swings the armature 37 to retnacted position, opening the valve seat member 15 for the bleed port member 2 and closing the valve seat memher for the bleed port member 3. When the pilot burner 45 is ignited, theheat of its flame on the single hot junction of the thermocouple 50 energizes the operator sufiiciently to move the armature 37 to attracted position with accompanying movement of the valve seat member 15 for the bleed port member 2 to closed position and movement of the valve seat member for the bleed port member 3 to open position.

With a core structure for the operator as herein specifically described, the air gap between the pole faces of the pole pieces 21 and 22 and the armature 37, when the armature is in retracted position, may be of the order of from about .015 to .017 of an inch. This is merely illustrative and in nowise limiting in so far as the appended claims are concerned.

While the valve members of the particular device illustrated and described are for a pilot valve mechanism for controlling a diaphragm valve, it is to be understood that the present invention is not limited in this respect. These valve members are illustrative of a control member which may be in the form of a main valve member for a main burner, or in the form of a switch, or of any other desired form.

The embodiment of the invention shown in the drawings is for illustrative purposes only, and it is to be expressly understood that said drawings and the accompanying specification are not to be construed as a definition of the limits or scope of the invention, reference being had to the appended claims for that purpose.

I claim:

1. The method of manufacturing \an improved unitary low reluctance magnet core from magnetically permeable metallic core post and pole piece members, comprising the steps of forming a pole piece member with an opening of a shape complemental with and of a size tightly to re ceive an end portion of a core post member, inserting said end portion of said core post member into said opening in tight engagement therein, swaging said core post member end portion to expand the latter within said opening and efiect more intimate engagement of said members, heating the intimately engaged portions of said members, to a temperature less than the melting point thereof sufficient to join the grains of metal of said portions in a low reluctance connection so that said members are substantially in one piece, and then slowly cooling said members.

2. The method of manufacturing an improved unitary low reluctance U-shaped magnet core from magetioally permeable metallic core post and pole piece members, comprising the steps of forming a pole piece member with a pair of spaced openings each having a shape complemental with and a size tightly to receive an end portion of a separate core post member, inserting said end portions of said core post members into said openings respectively in tight engagement therein, swaging said core post member end portions to expand the latter within said opening and effect more intimate engagement of said members, heating the intimately engaged portions or". said members to a temperature less than the melting point thereof sufficient to join the grains of metal of said portions in a low reluctance connection so that said members are substantially in one U-shaped piece, and then slowly cooling said members.

3. The method of manufacturing an improved unitary low reluctance U-shaped magnet core from magnetically permeable metallic core post and pole piece members, comprising the steps of forming a first pole piece member with a pair of spaced openings each having a shape cornplemental with :and a size tightly to receive one end portion of a separate core post member, forming each of a pair of second pole piece members with an opening having a shape complemental with and a size tightly to receive the other end portion of a separate one of said'core post members, inserting said one end portions of said core post members into the respective openings in said first pole piece member in tight engagement therein, inserting said other end portions of said core post members into the respective openings in said second pole piece members in tight engagement therein, swaging said core post member end portions to expand the latter within said openings and effect more intimate engagement of said members, heating the intimately engaged portions of said members to a temperature less than the melting point thereof sufficient to join the grains of metal of said portions in a low reluctance connection so that said members are substantially in one U-shaped piece, and then slowly cooling said members.

4-. The method of manufacturing an improved unitary low reluctance magnet core from magnetically permeable metallic core post and pole piece members, comprising the steps of forming each of a pair of pole piece members with an opening of a shape complemental with land of a size tightly to receive a separate end portion of the same same core post member, inserting said end portions of said core post member respectively into said openings in tight engagement therein, gripping said core post member intermediate said end portions to prevent substantial deformation of said gripped portion and maintain a predetermined minimum spacing between said pole piece members, swaging both end portions of said core post member while the latter is so gripped to expand said end portions within said openings and effect more intimate engagement of said core post and pole piece members, heating the intimately engaged portions of said members to a temperature less than the melting point thereof sufiicient to join the grains of metal of said portions in a low reluctance connection so that said members are substantially in one piece, and then slowly cooling said members.

5. An improved unitary low reluctance core for use in an electromagnetic power unit operable on the power from a source of small electric energy, comprising at least one magnetically permeable metallic core post member,

a magnetically permeable metallic pole piece member formed with an opening of a shape coniplemental with and of a size tightly to receive an end portion of said core post member and in which said end portion is tightly received, the grains of metal of the engaged portions of said core post and pole piece members being joined in a low reluctance connection so that said members are substantially in one piece, said connection being characterized by swaging of said core post end portion within said opening, and then heating the swagedly joined portions of said members to and slowly cooling the latter from a predetermined temperature less than the melting point of said members.

6. An improved unitary low reluctance U-shaped core for use in an electromagnetic power unit operable on the power from a source of small electric energy, comprising a pair of magnetically permeable metallic core post mem' bers, and a magnetically permeable metallic pole piece member formed with a pair of spaced openings each having a shape complemental with and a size tightly to receive an end portion or" a separate one of said core post members, the respective core post end portions disposed within said opening with said core posts projecting from the same side of said pole piece member in parallel relation, the grains of metal of the engaged portions of said core post and pole piece members being joined in low reluceva es? tance connections so that said members are substantially in one U-shaped piece, said connection being characterized by swaging of said core post end portions Within said openings, and then heating the swagedly joined portions of said members to and slowly cooling the latter from a predetermined temperature less than the melting point of said members.

7. An improved unitary low reluctance U-shaped core for use in electromagnetic power unit operable on the power from a source of small electric energy, comprising a pair of magnetically permeable metallic core post mcmbers, a first magnetically permeable metallic pole piece member formed with a pair of openings each having a shape complemental with and a size tightly to receive one end portion of a separate one of: said core post members, the respective core post end portions being disposed Within said openings with said core posts projecting from the same side of said pole piece memher in parallel relation, a pair of second magnetically permeable pole piece members each having an opening of. a shape complemental with and of a size tightly to receive the other end portion of a separate one of said core post members and in which said other end portions are respectively disposed, the grains of metal of the engaged portions of said core post and pole piece members being joined in low reluctance connections so that said members are substantially in one piece, said connections being characterized by swaging of said core post end portions within said openings, and then heating the swagedly joined portions of said members to and slowly cooling the latter from a predetermined temperature less than the melting point of said members.

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